Current treatments of cancer and in particular solid tumors, comprise mainly of surgical intervention followed by radiation therapy and/or chemotherapy. Dunne-Daly CF, “Principles of radiotherapy and radiobiology”, Semin Oncol Nurs. 1999 November;15(4):250-9; Hensley M L et al., “American Society of Clinical Oncology clinical practice guidelines for the use of chemotherapy and radiotherapy protectants. ”, J Clin Oncol. 1999 October;17(10):3333-55.In conjunction with such therapies, toxic chemotherapeutic agents such as Gemcidabin, Vinblastine, Cisplatin, Fluorouracil, Gleevec, Methotrexate, which are unable to differentiate between normal and cancerous cells, are used. While effective, these and other toxic chemotherapeutic agents have done little to increase overall patient survival. Moreover, current treatments in general also failed to improve 5-year survival rate of cancer patients despite synergistic combination of chemotherapies and radiotherapies. Even anti-epidermal growth factor receptor agents, anti-angiogenic drugs and immuno and immuno-adjuvant therapy using drugs such as Rituximab, Erbitux and Herceptin have failed to significantly increase the 5-year survival rate of cancer patients. Furthermore, complete remission or disease free survival of cancer patient irrespective of cancer type have not been improved upon by any of the aforementioned therapies or synergistic combinations thereof.
One treatment modality investigated to improve disease-free survival rates or lead to complete remission is manipulation of cell-division cycle of cancerous cells. In particular, cycling tumor cells are generally more vulnerable to radio- and chemotherapies than non-cycling tumor cells because complex biochemical and biomolecular processes such as enzyme-dependent DNA replication, enzyme-dependent phosphorylation, signal cascades, association and dissociation of transcriptional activating molecular complexes, and formation and dissociation of macromolecular assemblies of cytostructural elements are required during cell cycling. By inducing tumor cells into a cell cycle phase, anti-metabolic agents that inhibit any of the complex biochemical processes such as ribonucleotide reductase (RNR) inhibitors, dihydrofolate reductase inhibitors or DNA polymerase inhibitors can be used to stop cell cycling and thereby prevent tumor proliferation.
However, known methods taking advantage of cell cycling are limited to synchronizing cell cycle arrest with sequential applications of a chemotherapeutic agent. For example, one known method arrests malignant cells within a S phase of the cell cycle with pyrimidine analogs followed by exposure to high concentrations of anti-metabolites. B. Bhutan et al., Cancer Res. 33:888-894 (1973). Few or no cells in the population can proceed beyond this point of detention after application of the anti-metabolite. W Vogel et al., Hum. Genet. 45:193-8 (1978).
Other efforts include methods of manipulating the cell-division cycle by altering the cell cycle distribution within the cell population. These protocols stimulate malignant cells from a dormant phase into a cell cycling phase thereby increasing their vulnerability to anti-metabolic drugs acting during the vulnerable DNA replication phase. H H Euler et al., Ann. Med. Inteme. (Paris) 145:296-302 (1994); B C Lampkin et al., J. Clin. Invest. 50:2204-14 (1971); Alama et al., Anticancer Res. 10:853-8 (1990). Conversely, other known methods prohibit normal cells from entering S phase thereby protecting normal cells from chemotactic drugs.
Still another known method of synchronizing cell cycle phase with chemotherapeutics is a so-called pulse dose chemotherapy described by R E Moran et al., Cancer Treat. Rep. 64:81-6, (1980). In this approach, leukemic tumor cells in mice were detained in a S phase of the cell cycle with an infusion of hydroxyurea. After the infusion, the cells were “released” to continue cell cycling wherein a “pulse” of a second agent (Ara-C) was given to the mice. The intent was to maximize impact of the second agent as the cycling cells were moving through the vulnerable cell cycle S-phase. However, the results indicated that while mice treated with Ara-C just after the hydroxyurea infusion showed improved survival, mice treated with Ara-C at later times after the hydroxyurea infusion did not show improved survival. Clearly, simply synchronizing cell cycling with a second agent acting non-simultaneously did not improve the action of the two agents.
Nevertheless, known methods taking advantage of cell cycle continue to seek an optimal but passive synergy between dosage, pharmacokinetics, sequence and scheduling.
It might be expected that confining a cell population to a vulnerable cell cycle phase where cells are specifically vulnerable to damage might shift the dynamics of cell killing toward greater efficiency with a greater reduction in side-effects by diminishing exposure to toxic drugs. However, actual experiments taking advantage of cell cycle arrest or static synchronization have been disappointing because known methods are unable to actually induce cells into a cell cycle. Rather, all the known methods simply time the synergistic combination of cell cycle arrest or static synchronization with the target cell population. Moreover, agents such as pyrimidine and hydroxyurea used to effect the cell cycle can cause damage to normal cells.
Another approach would, of course, be to induce the cells to enter into a cell cycle phase as opposed to arresting the cell cycle or synchronizing the cell cycle. However, as would be otherwise predicted from the art, inducing cells into cell cycling increases the risk of a rapidly growing and recurring tumor. But the continued failure of known compositions to improve disease-free survival rates or lead to complete remission suggests a need for inducing malignant cells into cell cycling in a manner that does not proliferate the tumor but increases the susceptibility of the residual tumor to follow-on treatment with radiation and/or chemotherapy.
Therefore, there is a need for methods for inducing tumor cells into a cell cycle selected from the group of (different phases of the cell cycle) G1, S, G2 and M where the new methods can be synergistically applied with chemotherapy, immuno-therapy and radiation therapy. There is also a need for pre-sensitizing cancer tumors in general along with the need for a new serum-free and mitogen-free cytokine mixture comprised of specific ratios of IL-1β to IL-2, TNF-α to IL-2, IFN-γ to IL-2 and GM-CSF to IL-2 that unexpectedly demonstrates far better efficacy over known compositions in inducing a tumor cells to enter a cell cycle phase or for pre-sensitizing a cancer.